Chemically produced toner and process therefor

ABSTRACT

A toner for developing an electrostatic image comprising toner particles which include a binder resin, a wax and a colorant, wherein the wax has a melting point of between 50 and 150° C., the wax exists in the toner particles in domains of 2 μm or less mean particle size and (a) the mean circularity of the toner particles as measured by a Flow Particle Image Analyser is at least 0.90; and (b) the shape factor, SF1, of the toner particles is at most 165. A process for the manufacture of said toner which comprises the following steps: providing a latex dispersion; providing a wax dispersion; providing a colorant dispersion; mixing the latex dispersion, wax dispersion and colorant dispersion; and causing the mixture to flocculate.

FIELD OF THE INVENTION

This invention relates to toners for use in the formation ofelectrostatic images, their process of manufacture, processes using themand to toner apparatus and components incorporating them. It furtherrelates to any electroreprographic apparatus, component of the apparatusand consumable for use with the apparatus, which comprises such a toner,and to methods of manufacturing of such electroreprographic apparatus,components and consumables.

BACKGROUND OF THE INVENTION

Toners for development of an electrostatic image are conventionallyproduced by melt kneading of a pigment, resin and other toneringredients, followed by pulverisation. Classification is then needed togenerate an acceptably narrow particle size distribution.

Recently attention has been focussed on chemical routes to toners, wherea suitable particle size is not attained by a milling process, whichavoid the need for a classification step. By avoiding the classificationstep, higher yields can be attained, especially as the target particlesize is reduced. Lower particle size toners are of considerable interestfor a number of reasons, including better print resolution, lower pileheight, greater yield from a toner cartridge, faster or lowertemperature fusing, and lower paper curl.

Several routes to chemical toners have been exemplified. These includesuspension polymerisation, solution-dispersion processes and aggregationroutes. Aggregation processes offer several advantages including thegeneration of narrow particle size distributions, and the ability tomake toners of different shape. The toner shape is particularlyimportant in toner transfer from the organic photoconductor (OPC) to thesubstrate, and in cleaning of the OPC by a blade cleaner.

Several aggregation processes have been reported. U.S. Pat. No.4,996,127 (Nippon Carbide) reports a process in which black tonerparticles are grown by heating and stirring resin particles made byemulsion polymerisation with a dispersion of carbon black, where theresin contains acidic or basic polar groups. Numerous patents from Xerox(e.g. U.S. Pat. No. 5,418,108) describe a flocculation process whereparticles stabilised by anionic surfactants are mixed with particlesstabilised by cationic surfactants (or where a cationic surfactant isadded to particles stabilised by an anionic surfactant). U.S. Pat. No.5,066,560 and U.S. Pat. No. 4,983,488 (Hitachi Chemical Co.) describeemulsion polymerisation in the presence of a pigment, followed bycoagulation with an inorganic salt, such as magnesium sulphate oraluminium chloride. The applicants' own patent applications WO 98/50828and WO 99/50714, describe aggregation processes in which a surfactantused to stabilise the latex (i.e. the aqueous dispersion of the resin)and pigment is converted by a pH change from an ionic to a non-ionicstate, so initiating flocculation.

To form a permanent image on the substrate, it is necessary to fuse orfix the toner particles to the substrate. This is commonly achieved bypassing the unfused image between two rollers, with at least one of therollers heated. It is important that the toner does not adhere to thefuser rollers during the fixation process. Common failure modes includepaper wrapping (where the paper follows the path of the roller) andoffset (where the toner image is transferred to the fuser roller, andthen back to a different part of the paper, or to another paper sheet).One solution to these problems is to apply a release fluid, e.g. asilicone oil, to the fuser rollers. However this has many disadvantages,in that the oil remains on the page after fusing, problems can beencountered in duplex (double-sided) printing, and the operator mustperiodically re-fill the oil dispenser. These problems have led to ademand for so-called “oil-less” fusion, in which a wax incorporated inthe toner melts during contact of the toner with the heated fuserrollers. The molten wax acts as a release agent, and removes the needfor application of the silicone oil.

There are many problems associated with the inclusion of wax in a toner.Wax present at the surface of the toner may affect the triboelectriccharging and flow properties, and may reduce the storage stability ofthe toner by leading to toner blocking. Another problem frequentlyencountered is filming of the wax onto the metering blade anddevelopment rollers (for mono-component printers) or the carrier bead(for dual-component printers or copiers), and onto the photoconductordrum. Where contact charging and/or contact development are employed,and where cleaning blades or rollers are used, these can place an extrastress on the toner and make it more prone to filming. If the wax is notwell dispersed in the toner problems with transparency in colour tonerscan be found, and high haze values result. With conventional toners,prepared by the extrusion/pulverisation route, it has only provedpossible to introduce relatively small amounts of wax withoutencountering the above problems.

With colour toners, the demands on the toner to achieve oil-less releaseare much more severe than with monochrome printing. As typically fourcolours are used in full-colour printing, the mass of toner which can bedeposited per unit area is much higher than with black printing. Printdensities of up to around 2 mg/cm² may be encountered in colourprinting, compared with about 0.4-0.7 mg/cm² in monochrome prints. Asthe layer thickness increases it becomes more difficult to melt the waxand obtain satisfactory release at acceptable fusion temperatures andspeeds. Of course it is highly desirable to minimise the fusiontemperature, as this results in lower energy consumption and a longerfuser lifetime. With colour printing it is also important that printsshow high transparency. In addition it is necessary to be able tocontrol the gloss level. Inclusion of waxes in colour toners can havedetrimental effects on transparency, and can make it difficult to reachhigher gloss levels.

The efficiency of wax melting can be increased by reducing the waxmelting point. However this often leads to increased storage stabilityproblems, and in more pronounced filming of the OPC or metering blade.The domain size of the wax is also important, as this affects therelease, storage stability and transparency of the toner.

The release properties of the toner can also be affected by themolecular weight distribution of the toner, i.e. the resin thereof.Broader molecular weight distribution toners, which include a proportionof higher molecular weight (or alternatively cross-linked resin),generally show greater resistance to offset at higher fusiontemperatures. However, when large amounts of high molecular weightresins are included, the melt viscosity of the toner increases, whichrequires a higher fusion temperature to achieve fixation to thesubstrate and transparency. The haze values of the prints will then varyconsiderably with fusion temperature, with unacceptably high values atlow fusion temperatures. Haze may be assessed using a spectrophotometer,for example a Minolta CM-3600d, following ASTM D 1003.

Therefore the requirements for achieving an oil-less fusion coloursystem are severe. It is necessary to achieve a reasonably low fusiontemperature, with an acceptably wide release temperature window,including with high print densities. The prints must show goodtransparency with controllable gloss. The toner must not show blockingunder normal storage conditions, and must not lead to filming of the OPCor metering blade.

In addition it is important that the quality of the prints is maintainedover a long print run, and that the toner is efficiently used. Toachieve these goals there must be little development of the non-imageareas of the photoconductor (OPC) and the toner must show a hightransfer efficiency from the photoconductor to the substrate (or to anintermediate transfer belt or roller). If the transfer efficiency isclose to 100% it is possible to avoid the need for a cleaning step,where residual toner is removed from the photoconductor after transferof the image. However many electrophotographic devices contain amechanical cleaning device (such as a blade or a roller) to remove anyresidual toner from the photoconductor. Such residual toner may ariseeither from development of the non-image areas of the photoconductor, orfrom incomplete transfer from the photoconductor to the substrate orintermediate transfer belt or roller. A high transfer efficiency isespecially important for colour devices, where sometimes more than onetransfer step is required (for example from the photoconductor to atransfer belt or roller, and subsequently from the transfer belt orroller to the substrate).

It is known in the art that the shape of the toner can have a pronouncedeffect on its transfer and cleaning properties. Toners prepared byconventional milling techniques tend to have only moderate transferefficiencies due to their irregular shape. Spherical toners may beprepared by chemical routes, such as by suspension polymerisation or bylatex aggregation methods. These toners can transfer well, but theefficiency of cleaning with mechanical cleaning devices such as cleaningblades is low.

It is therefore desirable to produce a toner which can satisfy manyrequirements simultaneously. The toner should be capable of fixing tothe substrate at low temperatures by means of heated fusion rollerswhere no release oil is applied. The toner should be capable ofreleasing from the fusion rollers over a wide range of fusiontemperatures and speeds, and over a wide range of toner print densities.To achieve this it is necessary to include a wax or other internalrelease agent in the toner. This release agent must not causedetrimental effects on storage stability, print transparency or tonercharging characteristics, and must not lead to background development ofthe photoconductor (OPC). It must also not lead to filming of themetering blade or development roller (for a mono-component device) orthe carrier bead (for a dual- component device), or of thephotoconductor. In addition the shape of the toner must be controlled soas to give high transfer efficiency from the photoconductor to thesubstrate or intermediate transfer belt or roller, and from the transferbelt or roller (where used) to the substrate. If a mechanical cleaningdevice is used the shape of the toner must also be such as to ensureefficient cleaning of any residual toner remaining after image transfer.

Several patents exemplify aggregation processes where a single latex,made by a one-stage emulsion polymerisation process, is aggregated witha wax dispersion. Examples where a system based on counterionicsurfactants (i.e. an anionic and a cationic surfactant) is used includeU.S. Pat. No. 5,994,020 and U.S. Pat. No. 5,482,812 (both to Xerox).Examples where an inorganic coagulant is used include U.S. Pat. No.5,994,020, U.S. Pat. No. 6,120,967, U.S. Pat. No. 6,268,103 and U.S.Pat. No. 6,268,102 (all to Xerox). Mixed inorganic and organiccoagulants are used in U.S. Pat. No. 6,190,820 and U.S. Pat. No.6,210,853 (both to Xerox). U.S. Pat. No. 4,996,127 (Nippon Carbide)exemplifies a process in which a latex containing an acidic-functionalgroup is heated and stirred with a wax dispersion and carbon black togrow aggregate toner particles.

U.S. Pat. No. 5,928,830 (Xerox) discloses a two stage emulsionpolymerisation to make a core shell latex. The shell is made generallyof higher molecular weight and/or Tg than the core. The latex is thenmixed with pigment and flocculated through use of counterionicsurfactants. Inclusion of wax is not exemplified.

U.S. Pat. No. 5,496,676 (Xerox) discloses use of blends of differentlatexes with different molecular weight to increase the fusion latitude.Each latex is made by a single stage polymerisation. Toners were made byflocculating the mixed latexes with a pigment dispersion containing acounterionic surfactant. Inclusion of wax is not exemplified.

In U.S. Pat. No. 5,965,316 (Xerox) encapsulated waxes are made bycarrying out the emulsion polymerisation in the presence of a waxdispersion. These emulsion polymers containing wax are mixed with nonwax containing latexes of similar molecular weight, and toners madeusing a counterionic flocculation route.

JP 2000-35690 and JP 2000-98654 describe aggregation processes where anon-ionically stabilised dispersion of an ester-type wax is aggregatedwith mixed polymer emulsions of different molecular weight.

U.S. Pat. No. 5,910,389, U.S. Pat. No. 6,096,465 and U.S. Pat. No.6,214,510 (Fuji Xerox) disclose blends of resins with differentmolecular weights, incorporating hydrocarbon waxes of melting point ˜85°C. U.S. Pat. No. 6,251,556 (Fuji Xerox) also discloses blends of resins,as well as a two stage emulsion polymerisation to make a core shelllatex. The only wax which is incorporated is a high melting point (160°C.) polypropylene wax.

Control over the toner particle shape in aggregation processes has beendemonstrated. U.S. Pat. No. 5,501,935 and U.S. Pat. No. 6,268,102(Xerox) both exemplify spherical particles. Toners which arenon-spherical, but have low shape factors are disclosed in U.S. Pat. No.6,268,103 (Xerox); U.S. Pat. No. 6,340,549, U.S. Pat. No. 6,333,131,U.S. Pat. No. 6,096,465, U.S. Pat. No. 6,214,510 and U.S. Pat. No.6,042,979 (Fuji Xerox); and U.S. Pat. No. 5,830,617 and U.S. Pat. No.6,296,980 (Konica). Advantages of lower shape factors in improvingtransfer efficiency are shown in U.S. Pat. No. 6,214,510 and U.S. Pat.No. 6,042,979 (Fuji Xerox) and U.S. Pat. No. 5,830,617 (Konica). Otherreferences which disclose shape factors of toners are U.S. Pat. No.5,948,582, U.S. Pat. No. 5,698,354, U.S. Pat. No. 5,729,805, U.S. Pat.No. 5,895,151, U.S. Pat. No. 6,308,038, U.S. Pat. No. 5,915,150 and U.S.Pat. No. 5,753,396. However, none of these references discloses a tonerfor use in a mono-component electroreprographic apparatus which iscapable of demonstrating: release from oil-less fusion rollers over awide range of fusion temperature and print density; high transparencyfor OHP slides over a wide range of fusion temperature and printdensity; high transfer efficiency and the ability to clean any residualtoner from the photoconductor, and the absence of filming of themetering blade, development roller and photoconductor over a long printrun.

SUMMARY OF THE INVENTION

Therefore, obtaining a suitable toner, and a process for making it,which meets all the above requirements is difficult and requires carefulselection of the many possible components and parameters, each of whichhas constraints imposed on its physical and chemical properties by thefinal parameters of the system.

According to the present invention there is provided a toner fordeveloping an electrostatic image comprising toner particles whichinclude a binder resin, a wax and a colorant, wherein the wax has amelting point of between 50 and 150° C., the wax exists in the tonerparticles in domains of 2 μm or less mean particle size and (a) the meancircularity of the toner particles as measured by a Flow Particle ImageAnalyser is at least 0.90; and (b) the shape factor, SF1, of the tonerparticles is at most 165.

The mean circularity of the toner particles as measured by a FlowParticle Image Analyser is preferably at least 0.93, more preferably atleast 0.94. The mean circularity of the toner particles is preferablyless than 0.99. A particularly preferred range is 0.94-0.96.

The shape factor, SF1 (as hereinafter defined), of the toner particlesis preferably at most 155, more preferably at most 150, still morepreferably at most 145. SF1 is preferably at least 105. A particularlypreferred range of SF1 is from 130 to 150 and most particularlypreferred is from 135 to 145.

The shape factor, SF2 (as hereinafter defined), of the toner particlesis preferably at most 155, more preferably at most 145, even morepreferably at most 140, still even more preferably at most 135. SF2 ispreferably at least 105. A particularly preferred range of SF2 is from120-140, and most particularly preferred is 125-135.

The smoothness of the toner after the coalescence stage may be assessedby measuring the surface area of the toner, for example by the BETmethod. It is preferred that the BET surface area of the unformulatedtoner is in the range 0.5-2.0 m²/g, preferably 0.6-1.3 m²/g, morepreferably 0.7-1.1 m²/g, still more preferably 0.9-1.0 m²/g. Byunformulated is meant the toner prior to any optional blending withsurface additives.

The average size of the toner particles is preferably in the range from4-10 μm.

Toner having the above shape properties has been found to have hightransfer efficiency from the photoconductor to a substrate (or to anintermediate transfer belt or roller), in some cases close to 100%transfer efficiency.

We have found that it is possible to incorporate wax in relatively highamounts (e.g. about 5-15 wt %) without problems of blocking or filming,and without adverse effects on toner flow or tribocharge, or on printtransparency. The wax is present in the toner in domains of meandiameter 2 μm or less, preferably 1.5 μm or less. Preferably, the waxdomains are of mean diameter 0.5 μm or greater. Preferably the wax isnot substantially present at the surface of the toner. The relativelyhigh wax levels allow oil-less release even at high print densities,without requiring excessive amounts of high weight average molecularweight (M_(w)) resin. This allows fixation at low temperatures, and hightransparency across a range of fusion temperatures.

The resin may have a ratio of weight average molecular weight (Mw) tonumber average molecular weight (Mn) of at least 3, preferably at least5, more preferably at least 10.

Preferably, to achieve satisfactory oil-less release at hightemperatures, the polymer chains present in the binder resin encompass awide range of molecular weights. This can be achieved either by mixingresin particles of widely different molecular weight, or by synthesisinga latex (i.e. an aqueous dispersion of resin) for preparing the binderresin, e.g. by an aggregation process, containing a broad molecularweight distribution. A combination of both approaches can be used.

Latexes for preparing the binder resin may be made by polymerisationprocesses known in the art, preferably by emulsion polymerisation. Themolecular weight can be controlled by use of a chain transfer agent(e.g. a mercaptan), by control of initiator concentration or by heatingtime. Preferably, the binder resin is prepared from at least one latexcontaining a resin having a monomodal molecular weight distribution andat least one latex containing a resin having a bimodal molecular weightdistribution. By a resin with a monomodal molecular weight distributionis meant one in which the gpc spectrum shows only one peak. By a resinwith a bimodal molecular weight distribution is meant one where the gpcchromatogram shows two peaks, or a peak and a shoulder. Latexes with abimodal molecular weight distribution may be made using a two-stagepolymerisation. Preferably a higher molecular weight resin is madefirst, then in a second stage, a lower molecular weight resin is made inthe presence of the first resin. As a result, a bimodal molecular weightdistribution resin is made containing both low and high molecular weightresins. This may then be mixed with a monomodal low molecular weightresin. In a further aspect of the invention, three latexes can be used,where preferably at least two of these are of resins which show bimodalmolecular weight distributions. In a further preference, the secondbimodal resin in the latexes is of higher molecular weight than thefirst.

Preferably, the monomodal molecular weight resin contained in the latexis a low molecular weight resin and has a number average molecularweight of from 3000 to 10000, more preferably from 3000 to 6000. Wherethe binder resin is prepared from one bimodal resin contained in a latex(in addition to the monomodal resin in a latex), the bimodal resinpreferably has a weight average molecular weight of from 100,000 to500,000, more preferably from 200,000 to 400,000. Where the binder resinis prepared from more than one bimodal resin contained in a latex (inaddition to the monomodal resin in a latex), one bimodal resin mayoptionally have a weight average molecular weight from 500,000 to1,000,000 or more (e.g. in addition to the bimodal resin having a weightaverage molecular weight of from 100,000 to 500,000).

The higher molecular weight resins may also contain cross-linkedmaterial by inclusion of a multifunctional monomer (e.g. divinylbenzeneor a multi-functional acrylate) It is preferred that the overallmolecular weight distribution of the toner resin shows Mw/Mn of 3 ormore, more preferably 5 or more, most preferably 10 or more. The Tg ofeach resin is preferably from 30 to 100° C., more preferably from 45 to75° C., most preferably from 50 to 70° C. If the Tg is too low, thestorage stability of the toner will be reduced. If the Tg is too high,the melt viscosity of the resin will be raised, which will increase thefixation temperature and the temperature required to achieve adequatetransparency. It is preferred that all the components in the resin havea substantially similar Tg.

The resin may include one or more of the following preferred monomersfor emulsion polymerisation: styrene and substituted styrenes; acrylateand methacrylate alkyl esters (e.g. butyl acrylate, butyl methacrylate,methyl acrylate, methyl methacrylate, ethyl acrylate or methacrylate,octyl acrylate or methacrylate, dodecyl acrylate or methacrylate etc.);acrylate or methacrylate esters with polar functionality, for examplehydroxy or carboxylic acid functionality, hydroxy functionality beingpreferred (particularly 2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate, or hydroxy-terminated poly(ethylene oxide) acrylates ormethacrylates, or hydroxy-terminated poly(propylene oxide) acrylates ormethacrylates), examples of monomers with carboxylic acid functionalityincluding acrylic acid and beta-carboxyethylacrylate; vinyl typemonomers such as ethylene, propylene, butylene, isoprene and butadiene;vinyl esters such as vinyl acetate; other monomers such asacrylonitrile, maleic anhydride, vinyl ethers. The binder resin maycomprise a co-polymer of two or more of the above monomers.

Preferred resins are copolymers of (i) a styrene or substituted styrene,(ii) at least one alkyl acrylate or methacrylate and (iii) anhydroxy-functional acrylate or methacrylate.

The resin may be prepared from the following, not used in emulsionpolymerisation: dispersions of polyesters, polyurethanes, hydrocarbonpolymers, silicone polymers, polyamides, epoxy resins etc.

Preferably, the latex as above described is a dispersion in water.Optionally for a preferred process, the latex dispersion furthercomprises an ionic surfactant; preferably the surfactant present on thedispersions contains a group which can be converted from an ionic to anon-ionic form by adjustment of pH. Preferred groups include carboxylicacids or tertiary amines. Preferably, the ionic surfactant has a chargeof the same sign (anionic or cationic) as that of the surfactant used inthe wax and colorant dispersions described below. Optionally a non-ionicsurfactant may also be incorporated into the latex dispersion.

The wax should have a melting point (mpt) (as measured by the peakposition by differential scanning calorimetry (dsc)) of from 50 to 150°C., preferably from 50 to 130° C., more preferably from 50 to 110° C.,especially from 65 to 85° C. If the mpt is >150° C. the releaseproperties at lower temperatures are inferior, especially where highprint densities are used. If the mpt is <50° C. the storage stability ofthe toner will suffer, and the toner may be more prone to showingfilming of the OPC or metering blade.

In a further embodiment of the invention, for preparing the toner, thewax is made as a dispersion in water, preferably stabilised with anionic surfactant. The ionic surfactant is selected from the same classesas described above for the latex dispersion; preferably, the ionicsurfactant has the same sign (anionic or cationic) as the surfactantused for the latex dispersion described above and the colorantdispersion described below. The mean volume particle size of the wax inthe dispersion is preferably in the range from 100 nm to 2 μm, morepreferably from 200 to 800 nm, most preferably from 300 to 600 nm, andespecially from 350 to 450 nm. The wax particle size is chosen such thatan even and consistent incorporation into the toner is achieved.

The wax should be present in the toner in domains, where the mean sizeof the domains is at most 2 μm, preferably 1.5 μm or less. If the meansize of the wax domains is >2 μm, the transparency of the printed filmmay be reduced, and the storage stability may decrease. The particlesize values given are those measured by a Coulter LS230 Particle SizeAnalyser (laser diffraction) and are the volume mean.

The wax may comprise any conventionally used wax. Examples includehydrocarbon waxes (e.g. polyethylenes such as Polywax™ 400, 500, 600,655, 725, 850, 1000, 2000 and 3000 from Baker Petrolite; paraffin waxesand waxes made from CO and H₂, especially Fischer-Tropsch waxes such asParaflint™ C80 and H1 from Sasol; ester waxes, including natural waxessuch as Carnauba and Montan waxes; amide waxes; and mixtures of these.Hydrocarbon waxes are preferred, especially Fischer-Tropsch and paraffinwaxes. It is especially preferred to use a mixture of Fischer-Tropschand Carnauba waxes, or a mixture of paraffin and Carnauba waxes.

The amount of wax incorporated in the toner is preferably from 1 to 30wt % based on the total weight of the base toner composition (i.e. thetoner particles prior to any blending with a surface additive), morepreferably from 3 to 20 wt %, especially from 5 to 15 wt %. If the levelof wax is too low, the release properties will be inadequate foroil-less fusion. Too high a level of wax will reduce storage stabilityand lead to filming problems. The distribution of the wax through thetoner is also an important factor, it being preferred that wax issubstantially not present at the surface of the toner.

Advantageously, the toner is capable of fixing to the substrate at lowtemperatures by means of heated fusion rollers where no release oil isapplied and is capable of releasing from the fusion rollers over a widerange of fusion temperatures and speeds, and over a wide range of tonerprint densities. Furthermore, it has been found that the toner accordingto the invention does not lead to background development of thephotoconductor (OPC) and does not lead to filming of the metering bladeor development roller (for a mono-component device) or the carrier bead(for a dual-component device), or of the photoconductor.

Advantageously, the haze values of prints using the toner of theinvention do not vary considerably with fusion temperature. Haze may beassessed using a spectrophotometer, for example a Minolta CM-3600d,following ASTM D 1003. Preferably, the haze at a print density of 1.0mg/cm² is below 40, preferably below 30, and the ratio of the values atfusion temperatures of 130 and 160° C. is preferably at most 1.5, morepreferably at most 1.3 and most preferably at most 1.2.

Accordingly, the invention in another aspect provides a process forforming an image, the process comprising developing an electrostaticimage using a toner according to the invention, wherein the haze at aprint density of 1.0 mg/cm² is below 40, and the ratio of the values atfusion temperatures of 130 and 160° C. is at most 1.5 , preferably atmost 1.3 and more preferably at most 1.2. The fusion speed in theprocess may be at least 10 A4 size pages per minute, preferably at least20 A4 pages per minute.

The colorant is preferably present in an amount from 1-15 wt % of thetotal base toner composition (i.e. the toner particles prior to anyblending with a surface additive), more preferably 1.5-10 wt %, mostpreferably 2-8 wt %. These ranges are most applicable for organic,non-magnetic pigments. If, e.g., magnetite was used as a magneticfiller/pigment, the level would typically be higher. Preferably thecolorant comprises a pigment or blend of pigments. Any suitable pigmentcan be used, including black and magnetic pigments. For example carbonblack, magnetite, copper phthalocyanine, quinacridones, xanthenes, mono-and dis-azo pigments, naphthols etc. Examples include Pigment Blue 15:3,Red 31, 57, 81, 122, 146, 147 or 184; Yellow 12, 13, 17, 74, 180 or 185.Preferably, in an embodiment for preparing the toner, the colorant ismilled with an ionic surfactant, and optionally a non-ionic surfactantuntil the particle size is reduced, preferably to <300 nm, morepreferably <100 nm. In full colour printing it is normal to use yellow,magenta, cyan and black toners. However it is possible to make specifictoners for spot colour or custom colour applications. When the colorantis milled with an ionic surfactant, the surfactant is preferablyselected from the same classes of surfactant described above for thelatex (binder resin) and the wax; more preferably the surfactant has thesame sign as both the surfactants used above. The colorant dispersion isalso preferably a dispersion in water.

The toner as described above may additionally optionally comprise acharge control agent (CCA); preferably the charge control agent has beenmilled with the colorant. Suitable charge control agents are preferablycolourless, however coloured charge control agents may be used.Preferably, they include metal complexes, more preferably aluminium orzinc complexes, phenolic resins etc. Examples include Bontron™ E84, E88,E89 and F21 from Orient; Kayacharge N1, N3 and N4 from Nippon Kayaku;LR147 from Japan Carlit; TN-105 from Hodogaya. These can be milled in asimilar manner to the pigment. Where the CCA is added externally, asuitable high-speed blender may be used, e.g. a Nara Hybridiser.Alternatively, the CCA may be added as part of the pre-flocculationmixture, preferably as a wet cake.

The toner may have one more surface additives, as described below, e.g.to improve powder flow properties of the toner.

Preferably, the toner is made by a process which comprises flocculatinga dispersion of the resin (i.e. a latex), a dispersion of the wax and adispersion of the colorant, followed by heating and stirring to formcomposite particles containing the resin, wax and colorant, and thencoalescing these particles above the Tg of the resin to form the tonerparticles. Preferably the coalescence stage is controlled, such that thefeatures of the toner such as the wax domain size and the toner particleshape are achieved.

We have found that by using an aggregation process with particular waxdispersions, it is possible to incorporate wax in relatively highamounts as aforementioned.

According to the present invention, there is also provided a process forthe manufacture of a toner according to the above which comprises thefollowing steps:

-   -   i. providing a latex dispersion (i.e. containing resin        particles);    -   ii. providing a wax dispersion;    -   iii. providing a colorant dispersion;    -   iv. mixing the latex dispersion, wax dispersion and colorant        dispersion; and    -   v. causing the mixture to flocculate.

All of the features of the toner of the invention, particularly inregard to the resin or latex, wax, colorant and optional charge controlagent are also applicable to the process.

The process may further comprise, prior to step iv, the additional stepof providing a charge control agent component, which component may thenbe incorporated in step iv by mixing. The charge control agent may bemilled with the colorant.

Preferably, each dispersion is a dispersion in water.

The latex dispersion preferably comprises an ionic surfactant. Morepreferably the preparation of the latex dispersion comprises mixingtogether at least one latex with monomodal molecular weight distributionand at least one latex with bimodal molecular weight distribution. Thepreparation of the latex with bimodal molecular weight distributionpreferably comprises the successive steps of formation of a resin ofhigh molecular weight distribution followed by formation of a resin oflow molecular weight distribution such that the resulting latexcomprises composite particles comprising both the said low molecularweight resin and the said high molecular weight resin. The preparationof the wax dispersion in such a process preferably comprises the mixingtogether of the wax with an ionic surfactant. The preparation of thecolorant dispersion in such a process preferably comprises the millingtogether of the colorant with an ionic surfactant.

It is preferred that the dispersions of latex, colorant, charge controlagent where present, and wax have the same sign charge on thesurfactant. This enables individual components to be well mixed prior toflocculation. It is further preferred to use the same surfactant foreach of the individual dispersions. The mixed dispersions are thenflocculated in step (v). Any suitable method could be used, e.g.addition of an inorganic salt, an organic coagulant, or by heating andstirring. In a preferred method, the surfactant present on thedispersions contains a group which can be converted from an ionic to anon-ionic form and vice versa by adjustment of pH. In a preferredexample, the surfactant may contain a carboxylic acid group, and thedispersions may be mixed at neutral to high pH. Flocculation may then beeffected by addition of an acid, which converts the surfactant fromanionic to non-ionic. Alternatively the surfactant can be the acid saltof a tertiary amine, used at low pH. Flocculation may then be effectedby addition of a base which converts the surfactant from cationic tonon-ionic form. The flocculation step is preferably carried out belowthe Tg of the resin, but the mixed dispersions may be heated prior toflocculation. Such processes as described above, allow a very efficientuse of surfactant, and the ability to keep overall surfactant levelsvery low. This is advantageous since residual surfactant can beproblematic, especially in affecting the charging properties of thetoner, particularly at high humidity. In addition, such processes avoidthe need for large quantities of salt, as required for many prior artprocesses, which would need to be washed out.

After the flocculation step (v), the process as described above mayoptionally comprise heating, and optionally stirring, the flocculatedmixture to form loose aggregates, i.e. composite particles, of particlesize from 3 to 20 μm. Once the correct particle size is established, theaggregates may be stabilised against further growth. This may beachieved, for example, by addition of further surfactant, and/or by achange in pH. The temperature may then be raised above the Tg of theresin to bring about coalescence of the particles within each aggregateto form coalesced toner particles. During this step the shape of thetoner may be controlled through selection of the temperature and theheating time.

The shape of the toner may be measured by use of a Flow Particle ImageAnalyser (Sysmex FPIA) and by image analysis of images generated byscanning electron microscopy (SEM).

The circularity is defined as the ratio:Lo/Lwhere Lo is the circumference of a circle of equivalent area to theparticle, and L is the perimeter of the particle itself.

The shape factor, SF1, is defined as:

SF1=(ML)²/A×π/4×100, where ML=maximum length across toner, A=projectedarea

The shape factor, SF2, is defined as:

SF2=P²/A×¼π×100, where P=the perimeter of the toner particle,A=projected area An average of approximately 100 particles is taken todefine the shape factors for the toner.

SF1 is a measure of the deviation from a spherical shape (SF1 of 100being spherical). SF2 is a measure of the surface smoothness.

If the toner is designed for a printer or copier which does not employ amechanical cleaning device, it may be preferred to coalesce the toneruntil a substantially spherical shape is attained. If, however, thetoner is designed for use in a printer or copier in which a mechanicalcleaning device is employed to remove residual toner from thephotoconductor after image transfer, it may be preferred to select asmooth off-spherical shape, where the mean circularity is in the range0.90-0.99, preferably 0.93-0.99, more preferably 0.94-0.99, still morepreferably 0.94-0.96, where SF1 is 105-165, preferably 105-155, morepreferably 105-150, still more preferably 105-145 and where SF2 is105-155, preferably 105-145, more preferably 105-140, still morepreferably 105-135. The SF1 is particularly preferably 130-150 and mostparticularly preferred of all 135-145. SF2 is particularly preferably120-140, and most particularly preferred of all 125-135. Preferably,SF1>SF2. The ratio SF1/SF2 is preferably from 1.05 to 1.15, morepreferably from 1.07 to 1.13, still more preferably from 1.08 to 1.12.

The smoothness of the toner after the coalescence stage may also beassessed by measuring the surface area of the toner, for example by theBET method. It is preferred that the BET surface area of theunformulated toner is in the range 0.5-2.0 m²/g, preferably 0.6-1.3m²/g, more preferably 0.7-1.1 m²/g, still more preferably 0.9-1.0 m²/g.By unformulated is meant the toner prior to any optional blending withsurface additives.

Advantageously, the manner of making the toner according to the processof invention enables the shape of the toner to be controlled so as togive both high transfer efficiency from the photoconductor to thesubstrate or intermediate transfer belt or roller, and from the transferbelt or roller (where used) to the substrate, as well as to ensureefficient cleaning of any residual toner remaining after image transfer.

The cooled dispersion of coalesced toner particles is then optionallywashed to remove surfactant, and then optionally dried.

The toner particles may then be blended with one or more surfaceadditives to improve the powder flow properties of the toner, or to tunethe tribocharge properties. Typical surface additives include, but arenot limited to, silica, metal oxides such as titania and alumina,polymeric beads (for example acrylic or fluoropolymer beads) and metalstearates (for example zinc stearate). Conducting additive particles mayalso be used, including those based on tin oxide (e.g. those containingantimony tin oxide or indium tin oxide). The additive particles,including silica, titania and alumina, may be made hydrophobic, e.g. byreaction with a silane and/or a silicone polymer. Examples ofhydrophobising groups include alkyl halosilanes, aryl halosilanes, alkylalkoxysilanes (e.g. butyl trimethoxysilane, iso-butyl trimethoxysilaneand octyl trimethoxysilane), aryl alkoxysilanes, hexamethyldisilazane,dimethylpolysiloxane and octamethylcyclotetrasiloxane. Otherhydrophobising groups include those containing amine or ammonium groups.Mixtures of hydrophobising groups can be used (for example mixtures ofsilicone and silane groups, or alkylsilanes and aminoalkylsilanes.)Examples of hydrophobic silicas include those commercially availablefrom Nippon Aerosil, Degussa, Wacker-Chemie and Cabot Corporation.Specific examples include those made by reaction withdimethyldichlorosilane (e.g. Aerosil™ R972, R974 and R976 from Degussa);those made by reaction with dimethylpolysiloxane (e.g. Aerosil™ RY50,NY50, RY200, RY200S and R202 from Degussa); those made by reaction withhexamethyldisilazane (e.g. Aerosil™ RX50, NAX50, RX200, RX300, R812 andR812S from Degussa); those made by reaction with alkylsilanes (e.g.Aerosil™ R805 and R816 from Degussa) and those made by reaction withoctamethylcyclotetrasiloxane (e.g. Aerosil™ R104 and R106 from Degussa).

The primary particle size of the silicas used is typically from 5 to 100nm, preferably from 7 to 50 nm. The BET surface area of the silicas maybe from 20 to 350 m²/g, preferably 30-300 m²/g. Combinations of silicaswith different particle size and/or surface area may be used. Preferredexamples of combinations of silicas with different primary particle sizeare: Aerosil™ R972 or R812S (Degussa), or HDK™ H15 or H30 (Wacker); withAerosil™ RX50, RY50 (Degussa) or HDK™ H05TD, H05TM or H05TX (Wacker).Each additive may be used at 0.1-5.0 wt % based on toner, preferably0.2-3.0 wt %, more preferably 0.25-2.0 wt %. It is possible to blend thedifferent size additives in a single blending step, but it is oftenpreferred to blend them in separate blending steps. In this case, thelarger additive may be blended before or after the smaller additive. Itmay further be preferred to use two stages of blending, where in atleast one stage a mixture of additives of different particle size isused. For example, an additive with low particle size may be used in thefirst stage, with a mixture of additives of different particle size inthe second step. Examples would include use of Aerosil™ R812S or R972,or HDK™ H15 or H30 in the first step, along with a mixture containingone of these additives with a larger additive (such as Aerosil™ RX50 orRY50, or HDK™ H05TD, H05TM or H05TX) in the second step. In such a caseit would be preferred to use 0.2-3.0 wt %, preferably 0.25-2.0 wt % ofthe smaller additive in the first step, and 0.1 to 3.0 wt %, preferably0.2 to 2.0 wt % of each of the additives in the second step.

Where titania is used, it is preferred to use a grade which has beenhydrophobised, e.g. by reaction with an alkylsilane and/or a siliconepolymer. The titania may be crystalline or amorphous. Where crystallineit may consist of rutile or anatase structures, or mixtures of the two.Examples include grades T805 or NKT90 from Nippon Aerosil.

Hydrophilic or hydrophobic grades of alumina may be used. A preferredgrade is Aluminium Oxide C from Degussa.

It is often preferred to use combinations of silica and titania (e.g.R972, H15, R812S or H30 with NKT90), or of silica, titania and alumina(e.g. R972, H15, R812S or H30 with NKT90 and Aluminium Oxide C).Combinations of large and small silicas, as described above, can be usedin conjunction with titania, alumina, or with blends of titania andalumina.

Preferred formulations of surface additives include those in thefollowing list: hydrophobised silica;

large and small particle size silica combinations, which silicas may beoptionally hydrophobised;

hydrophobised silica and one or both of hydrophobised titania andhydrophilic or hydrophobised alumina;

large and small particle size silica combinations as described above andone or both of hydrophobised titania and hydrophilic or hydrophobisedalumina.

Polymer beads or zinc stearate may be used to improve the transferefficiency or cleaning efficiency of the toners. Charge control agentsmay be added in the external formulation (i.e. surface additiveformulation) to modify the charge level or charging rate of the toners.

The total level of surface additives used may be from about 0.1 to about10 wt %, preferably from about 0.5 to 5%, based on the weight of thebase toner, i.e. prior to addition of the surface additive. Theadditives may be added by blending with the toner, using, for example, aHenschel blender, a Nara Hybridiser, or a Cyclomix blender (Hosokawa).

The toner may be used as a mono-component or a dual component developer.In the latter case the toner is mixed with a suitable carrier bead.

The invention is particularly suitable for use in an electroreprographicapparatus or method where one or more of the following hardwareconditions of an electroreprographic device applies:

i) where the device contains a developer roller and metering blade (i.e.where the toner is a monocomponent toner);

ii) where the device contains a cleaning device for mechanicallyremoving waste toner from the photoconductor;

iii) where the photoconductor is charged by a contact charging means;

iv) where contact development takes place or a contact developmentmember is present;

v) where oil-less fusion rollers are used;

vi) where the above devices are four colour printers or copiers,including tandem machines

Advantageously, the invention provides a toner which satisfies manyrequirements simultaneously. The toner is particularly advantageous foruse in a mono-component electroreprographic apparatus and is capable ofdemonstrating: release from oil-less fusion rollers over a wide range offusion temperature and print density; high transparency for OHP slidesover a wide range of fusion temperature and print density; high transferefficiency and the ability to clean any residual toner from thephotoconductor, and the absence of filming of the metering blade,development roller and photoconductor over a long print run.

In another aspect of the present invention, there is provided a processfor manufacturing an electroreprographic apparatus and/or a component ofthe apparatus and/or a consumable for use with the apparatus, theprocess using a toner as described above.

In yet another aspect of the present invention, there is provided anelectroreprographic apparatus, a component of the apparatus and/or aconsumable for use with the apparatus, which comprises a toner asdescribed above.

All weights referred to herein are percentages based on the total weightof the toner, unless otherwise stated.

The invention will now be illustrated by the following Examples, whichare non-limiting on the invention.

1. Preparation of Latexes

1.1. Synthesis of Latex a-1

A low molecular weight resin was synthesised by emulsion polymerisation.The monomers used were styrene (83.2 wt %), 2-hydroxyethyl methacrylate(3.5 wt %) and acrylic ester monomers (13.3 wt %). Ammonium persulphate(0.5 wt % on monomers) was used as the initiator, and a mixture of thiolchain transfer agents (4.5 wt %) was used as chain transfer agents. Thesurfactant was Akypo™ (a carboxylated alkyl ethoxylate, i.e. acarboxy-functional surfactant) RLM100 (available from Kao, 3.0 wt % onmonomers). The emulsion had a particle size of 93 nm, and a Tg midpoint(as measured by differential scanning calorimetry (dsc)) of 55° C. GPCanalysis against polystyrene standards showed the resin to haveMn=6,500, Mw=14,000, Mw/Mn=2.2. The solids content was 30 wt %.

1.2. Synthesis of Latex a-2

A latex was made in a similar manner to Latex a-1, except the level ofstyrene was 90.4 wt % and the level of acrylic ester monomers was 6.1 wt%. The amount of 2-hydroxyethyl methacrylate (3.5 wt %) remained thesame. The emulsion had a particle size of 88 nm, and a Tg midpoint (asmeasured by differential scanning calorimetery (dsc)) of 65° C. GPCanalysis against polystyrene standards showed the resin to haveMn=5,100, Mw=12,800, Mw/Mn=2.5. The solids content was 30 wt %.

1.3. Synthesis of Latex a-3

A latex was made in a similar manner to Latex a-1, except the level ofstyrene was 90.4 wt % and the level of acrylic ester monomers was 6.1 wt%. The amount of 2-hydroxyethyl methacrylate (3.5 wt %) remained thesame. The emulsion had a particle size of 91 nm, and a Tg midpoint (asmeasured by differential scanning calorimetry (dsc)) of 65° C. GPCanalysis against polystyrene standards showed the resin to haveMn=5,100, Mw=13,000, Mw/Mn=2.6. The solids content was 30 wt %.

1.4. Synthesis of Latex b-1

A bimodal molecular weight distribution latex was made by a two-stagepolymerisation process, in which the higher molecular weight portion wasmade in the absence of chain transfer agent, and in which the molecularweight of the lower molecular weight portion was reduced by use of 2.5wt % of mixed thiol chain transfer agents. Ammonium persulphate (0.5 wt% on monomers) was used as the initiator, and the surfactant was Akypo™RLM100 (available from Kao, 3 wt % on monomers).

The monomer composition for the low molecular weight portion was styrene(82.5%, 2-hydroxyethyl methacrylate (2.5%) and acrylic ester monomers(15.0%). The overall monomer composition was styrene (73.85 wt %),2-hydroxyethyl methacrylate (6.25 wt %) and acrylic ester monomers (19.9wt %). The emulsion had a particle size of 78 nm and a Tg midpoint (asmeasured by dsc) of 67° C. GPC analysis against polystyrene standardsshowed a bimodal molecular weight distribution with Mn=30,000,Mw=249,000, Mw/Mn=8.3. The solids content was 40 wt %.

1.5. Synthesis of Latex b-2

A latex was made in a similar manner to Latex b-1. The emulsion had aparticle size of 79 nm, and a Tg midpoint (as measured by differentialscanning calorimetry (dsc)) of 66° C. GPC analysis against polystyrenestandards showed the resin to have Mn=31,000, Mw=252,000, Mw/Mn=8.1. Thesolids content was 40 wt %.

2. Pigment Dispersion

A dispersion of Pigment Red 122 (Hostaperm™ Pink E, Clariant) was used.The pigment was milled in water using a bead mill, with Akypo™ RLM100(Kao) and Solsperse™ 27000 (Avecia) (a polymeric dispersant) asdispersants. The pigment content of the dispersion was 22.1 wt %.

3. Wax Dispersion

An aqueous wax dispersion was used which contained an 80:20 mixture ofParaflint™ C80 (Fischer-Tropsch wax from Sasol) and Carnauba wax. Akypo™RLM 100 was used as the dispersant. The mean volume particle size of thewax was approximately 0.4 μm, and the solids content 25 wt %. Analysisby differential scanning calorimetry (dsc) of the dried dispersionshowed the wax to have a melting point (peak position from the dsctrace) of approximately 76° C.

4. Toner Preparation

4.1 Toner 1

Latex a-1 (7150 g), Latex b-1 (825 g) the wax dispersion (1429 g ), thepigment dispersion (475 g, containing 105 g Pigment Red 122) and a pasteof Bontron E88 (308 g, Orient, containing 60 g of Bontron E88) and water(19830 g) were mixed and stirred. The temperature was raised to 40° C.The mixed dispersions were circulated for 10 mins through a high shearmixer and back into the vessel. Then, as the material was circulating asolution of sulphuric acid was added into the high shear mixer to reducethe pH to 2.5. The temperature was then raised to 55° C., and stirringcontinued for 1 hr. A solution of sodium dodecybenzenesulphonate (750 gof a 10% solution) was added, and dilute sodium hydroxide solution wasadded to raise the pH to 7.3. The temperature was then raised to 120° C.and stirring continued for a further 80 mins. Coulter Counter™ analysisshowed the mean volume particle size was 8.7 μm and the final GSD was1.25. Microscopic analysis showed the toner particles to be of uniformsize and of smooth, off-spherical shape. Analysis with a Flow ParticleImage Analyser (Sysmex FPIA,) showed the mean circularity to be 0.95

The resultant magenta toner dispersion was filtered on a pressurefilter, and washed with water. The toner was then dried in an oven.Analysis by GPC against polystyrene standards, showed the toner resin tohave Mn=3,500, Mw=50,600, Mw/Mn=14.4.

Analysis by transmission electron microscopy (TEM) showed the presenceof wax domains in the toner, the domain size being approximately 1.0-1.5μm. BET surface area measurements showed the particles to have a surfacearea of 0.85 m²/g.

A portion of the toner was blended using a Prism blender with 0.5 wt %of Aerosil™ R812S (Degussa) hydrophobic silica. Analysis by SEM andimage analysis showed the mean SF1 value to be 133, and the 50% value(from the cumulative distribution curve) to be 129. The toner was thenprinted in a monocomponent monochrome printer which had been modified toremove the fuser, to allow printing of un-fused images. Unfused printsamples were prepared at 1.0 and 2.0 mg/cm² using multiple passesthrough the printer.

The images were then fused off-line using a QEA Fuser-Fixer equippedwith a pair of heated oil-less fuser rollers. The fuser speed was set to20 ppm for images printed on paper, and 10 ppm for images printed ontransparencies for an overhead projector. For the prints on both paperand transparency, no hot offset or paper wrapping was found to occur upto 175° C. (the maximum fusion temperature studied) The samples printedand fused on acetates were examined using a Minolta CM-3600d Haze Meter,according to ASTM D 1003. The results are shown in Table 1: TABLE 1 Haze% (H) Fusion temperature (° C.) 1 mg/cm² print density 2 mg/cm² printdensity 130 29.3 42.5 135 25.6 42.9 140 27.1 40.8 145 26.8 42.0 150 26.240.4 155 25.1 38.8 160 25.5 39.5 165 24.4 40.8 170 23.4 40.3 175 23.240.0 Haze ratio H₍₁₃₀₎/H₍₁₆₀₎ 1.15 1.08

As can be seen the samples show minimal variation in haze with fusiontemperature in the range studied.

A separate sample of the toner was then printed in a similar printer,but this time with the fuser unit installed. A print run of 1000 textprints was carried out, and the masses of both the consumed toner, andthe toner sent to the waste tray were measured. From this a usageefficiency figure, defined as[1-{(mass of toner sent to the waste tray)/(mass of tonerconsumed)}]×100was calculated. The value was 93%.

After a 3000 page print test there was found no noticeable backgrounddevelopment on the photoconductor, and no photoconductor filming.

4.2. Toners 2-7

Further Toners 2-7 were made by a similar process to that described forToner 1, except that the step of adding sodium dodecylbenzenesulphonateprior to the coalescence step was omitted. The latexes used for eachtoner are shown in Table 2. The toners contained 3.5 wt % Pigment Red122, and 2 wt % E88 CCA. The toner shape was controlled in each case bythe length of the coalescence process (heating above the latex Tg). Theaverage toner particle size (Coulter Counter™, aperture 100 μm), meancircularity (FPIA measurement) and BET surface area of the base toner(i.e. before blending with surface additive) were measured.

Each base toner was then blended with silica as surface additive toproduce formulated toner. Two different silica formulations (Type I andII) were used so that each base toner produced two formulated toners:

Type I: a low particle size hydrophobised silica (BET surface area 220m2/g)

Type II: a mixture of a low particle size hydrophobised silica (BETsurface area 220 m²/g) and a larger particle size hydrophobised silica(BET surface area approximately 50 m²/g).

The SF1 and SF2 values were then measured on Type I formulated toner.

The properties of the toners 2-7 are shown in Table 2. TABLE 2 BETAverage surface particle Mean area of size, circularity of SF1 of SF2 ofbase D_(v)50 base toner formulated formulated toner Toner Latexes (μm)from FPIA toner* toner* (m²/g) 2 a-2 b-2 8.1 0.91 152 150 1.5 3 a-2 b-27.9 0.95 142 128 0.9 4 a-3 b-2 8.2 0.96 111 118 0.7 5 a-2 b-2 6.8 0.91152 150 1.9 6 a-2 b-2 6.8 0.94 139 128 0.9 7 a-3 b-2 6.8 0.98 116 1170.9*measured on toners with Type I surface additive formulation

Transfer efficiency (TE) data was then recorded for transfer from theorganic photoconductor (OPC) of a monocomponent monochrome printer to atransparency substrate by measuring the mass of toner on the OPC and onthe substrate by vacuuming the toner into a filter which was weighed.Masses on the OPC were determined by crash-stopping the printer. Masseson the substrate were determined by stopping the print before the fuser.The control parameters of the printer were altered to develop differentprint densities, and the data in Table 3 below shows TE values for eachtoner recorded across a range of print densities. TABLE 3 Surface TonerAdditive Type Transfer Efficiency (%) OPC to substrate 2 I 94-96 2 II87-94 3 I  99-100 3 II 95-97 5 I 94 5 II 93-99 6 I  97-100 6 II ˜100

It can be seen that the non-spherical toners having the best transferefficiency are toners 3 and 6. In some cases the transfer efficiency isup to 100%. Toners 2 and 5 also have good but generally lower transferefficiency. The non-spherical toners also clean well from aphotoconductor using a mechanical cleaning device. Toners 4 and 7(results not shown) are the most spherical shape and these tonerstransfer from a photoconductor to a substrate well but efficiency ofcleaning from a photoconductor with a mechanical cleaning device islower than for the non-spherical toners.

Throughout the description and claims of this specification, the words“comprise” and “contain” and variations of the words, for example“comprising” and “comprises”, mean “including but not limited to”, andare not intended to (and do not) exclude other components.

Unless the context clearly indicates otherwise, plural forms of theterms herein are to be construed as including the singular form and viceversa.

It will be appreciated that variations to the foregoing embodiments ofthe invention can be made while still falling within the scope of theinvention. Each feature disclosed in this specification, unless statedotherwise, may be replaced by alternative features serving the same,equivalent or similar purpose. Thus, unless stated otherwise, eachfeature disclosed is one example only of a generic series of equivalentor similar features.

All of the features disclosed in this specification may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. In particular, thepreferred features of the invention are applicable to all aspects of theinvention and may be used in any combination. Likewise, featuresdescribed in non-essential combinations may be used separately (not incombination).

It will be appreciated that many of the features described above,particularly of the preferred embodiments, are inventive in their ownright and not just as part of an embodiment of the present invention.Independent protection may be sought for these features in addition toor alternative to any invention presently claimed.

1-55. (canceled)
 56. A toner for developing an electrostatic imagecomprising toner particles which include a binder resin, a wax and acolorant, wherein the wax has a melting point of between 50 and 150° C.,and the wax exists in the toner particles in domains of 2 μm or lessmean particle size and wherein (a) the mean circularity of the tonerparticles as measured by a Flow Particle Image Analyser is at least0.90; (b) the shape factor, SF1, of the toner particles is in the rangefrom 130 to 150; and (c) the ratio SF1/SF2 of the shape factor, SF1, tothe shape factor, SF2, is from 1.07 to 1.13.
 57. A toner according toclaim 56 wherein the mean circularity of the toner particles is in therange from 0.93 to 0.99.
 58. A toner according to claim 57 wherein themean circularity of the toner particles is in the range from 0.94 to0.96.
 59. A toner according to claim 56 wherein SF1 of the tonerparticles is at most
 145. 60. A toner according to claim 59 wherein SF1of the toner particles is in the range from 135 to
 145. 61. A toner fordeveloping an electrostatic image comprising toner particles whichinclude a binder resin, a wax and a colorant, wherein the wax has amelting point of between 50 and 150° C., and the wax exists in the tonerparticles in domains of 2 μm or less mean particle size and wherein (a)the mean circularity of the toner particles as measured by a FlowParticle Image Analyser is in the range from 0.94 to 0.96; (b) the shapefactor, SF1, of the toner particles is in the range from 135 to 145; and(c) SF1 >SF2.
 62. A toner according to claim 56 wherein SF2 of the tonerparticles is in the range from 120 to
 140. 63. A toner according toclaim 57 wherein SF2 of the toner particles is in the range from 125 to135.
 64. A toner according to claim 56 wherein the BET surface area ofthe particles is 0.7-1.1 m²/g.
 65. A toner according to claim 56 whereinthe wax exists in the toner in domains of mean diameter 1.5 μm or less.66. A toner according to claim 56 wherein the binder resin is preparedfrom at least one latex containing a resin having a monomodal molecularweight distribution and at least one latex containing a resin having abimodal molecular weight distribution.
 67. A toner according to claim 66wherein the monomodal molecular weight resin is a low molecular weightresin and has a number average molecular weight of from 3000 to 10000.68. A toner according to claim 66 wherein the bimodal resin has a weightaverage molecular weight of from 100,000 to 500,000.
 69. A toneraccording to claim 56 wherein the resin comprises a copolymer of (i) astyrene or substituted styrene, (ii) at least one alkyl acrylate ormethacrylate and (iii) an hydroxy-functional acrylate or methacrylate.70. A toner according to claim 56 wherein the amount of wax is from 3 to20 wt %.
 71. A toner according to claim 56 which further comprises acharge control agent.
 72. A process for forming an image, the processcomprising developing an electrostatic image using a toner according toclaim 56, wherein the haze at a print density of 1.0 mg/cm² is below 40,and the ratio of the values at fusion temperatures of 130 and 160° C. isat most 1.5.
 73. A process for the manufacture of a toner for developingan electrostatic image comprising toner particles which include a binderresin, a wax and a colorant, wherein the wax has a melting point ofbetween 50 to 150° C.; and the wax exists in the toner particles indomains of 2 μm or less mean particle size and wherein (a) the meancircularity of the toner particles as measured by a Flow Particle ImageAnalyser is at least 0.90; and (b) the shape factor, SF1, of the tonerparticles is at most 165, which process comprises the following steps:I. providing a latex dispersion which has at least one latex with amonomodal molecular weight distribution and has at least one latex witha bimodal molecular weight distribution; II. providing a wax dispersion;III. providing a colorant dispersion IV. mixing the latex dispersion,wax dispersion and colorant dispersion; and V. causing the mixture toflocculate.
 74. A process according to claim 73 wherein the monomodalmolecular weight latex has a number average molecular weight of from3000 to
 10000. 75. A process according to claim 74 wherein the monomodalmolecular weight latex has a number average molecular weight of from3000 to
 6000. 76. A process according to claim 73 wherein the bimodallatex has a weight average molecular weight of from 100,000 to 500,000.77. A toner according to claim 76 wherein the bimodal latex has a weightaverage molecular weight of from 200,000 to 400,000.
 78. A processaccording to claim 73 further comprising heating the flocculated mixtureobtained after step (v) to form loose aggregates of particle size from 3to 20 μm.
 79. A process according to claim 78 further comprising heatingthe aggregates to a temperature above the Tg of the latex to inducecoalescence to form toner particles.
 80. A process according to claim 73wherein the latex dispersion comprises an ionic surfactant.
 81. Aprocess according to claim 73 wherein the latex containing a resinhaving a bimodal molecular weight distribution is prepared by a processcomprising the successive steps of forming a polymer of high molecularweight distribution followed by forming a polymer of low molecularweight distribution such that the resulting latex comprises compositeparticles comprising both said low molecular weight polymer and saidhigh molecular weight polymer.
 82. A process according to claim 73which, prior to step iv, further comprises the step of providing acharge control agent dispersion, which dispersion is then incorporatedin step iv by mixing.
 83. A process according to claim 82 wherein thecharge control agent is milled with the colorant.
 84. A processaccording to claim 73 wherein the preparation of the wax dispersioncomprises the mixing together of the wax with an ionic surfactant.
 85. Aprocess according to claim 73 wherein the preparation of the colorantdispersion comprises the milling together of the colorant with an ionicsurfactant.
 86. A process according to claim 73 wherein the dispersionsof latex, colorant, wax, and charge control agent where present, havethe same sign charge on the surfactant.
 87. A process according to claim86 wherein the surfactant present in the dispersions contains a groupwhich can be converted from an ionic to a non-ionic form and vice versaby adjustment of pH.
 88. A toner for developing an electrostatic imagewhich has been obtained by the process of claim 73.